check_free_list returns a length, not bool.

Particularly useful for reproduction, like tdbtorture.

      
If a Swedish-speaking Finn writes code in English, why should I complain about
a few weird spellings?

(Was succeeding in finding "Free bucket 8" string, because of "Free bucket 80:".

Now we get long options!

The former encapsulates a common "just exit on error" case, the latter
avoids having to repeat the extra usage string.

(We actually would have crashed before if someone passed NULL there, even
 though the documentation said you could).

A little less typing for users.

compiler, list, noerr, sparse_bsearch, str, str_talloc, stringmap, talloc_link, tdb, tdb2, typesafe_cb: fix examples

Phew, now they call compile!

Now (with fixes) every ccanlint example compiles!

      
      /**
       * struct foo - some description
      
So, <identifier> here can have a space in it.

      
This hit my doc extraction tool, so fix it!

This is everything up to the list module... now it's time for sleep.

Including intuiting ccan depends based on headers...

In particular, we can assume "somefunc()" exists in our examples.

Try to glue consecutive examples together if all else fails (works well for
ccan/alloc/alloc.h).  This means we should put examples into list in order.

  
These are from hash: the entire example is indented, there is no main(), and
there are unused static functions.

Some of the compulsory tests don't have a total_score; treat that as "1".
And don't print out a score if the total is <= 1.

Don't assume that ../modulename.o already built!

And don't require the module.o to already exist: link against generated .o files.

Includes primitive attempt to place fragments into appropriate framework to
compile them.

We had example names like "example-opt.h-opt_parse", which got trimmed to
"example-opt".  By using a basename of example-opt.h-opt_parse.c, we only
strip the final ".c" not the middle ".h".

Don't allow NULL descs, and put them in macro.  Users can use "", but make
sure it's explicit, not an accidental omission.
Use errx() instead of assert() for API usage errors.
Rename opt_flags to opt_type.

I still don't like the duplication, but it's clearer and not much longer.